SiC, which is superior to Si, etc., in terms of heat resistance, mechanical strength, and the like, has been attracting attention as a new semiconductor material. Some single crystal SiC substrate may originally contain, in its surface, crystal defects or the like.
Patent Document 1 discloses a surface planarization method for planarizing (repairing) a surface of a single crystal SiC substrate. The surface planarization method includes forming a carbonized layer and a sacrificial growth layer on a single crystal SiC substrate, and etching the sacrificial growth layer, for surface planarization. This can produce a high-quality seed substrate for epitaxial growth. Patent Document 1 discloses performing etching under a high-vacuum condition.
In general, a seed crystal produced in the above-described manner is subjected to treatments including epitaxial growth, ion implantation, ion activation, and the like.
Patent Document 2 discloses a method for suppressing sublimation of Si and SiC during ion activation, by performing the ion activation after a carbon layer (graphene cap) is formed on a surface of a single crystal SiC substrate. In the method, subsequently, the carbon layer is removed, and the surface of the single crystal SiC substrate is etched to remove an insufficient ion-implanted portion.
The etching is performed for the purpose of removing a portion (insufficient ion-implanted portion) of the surface of the single crystal SiC substrate where the ion concentration is insufficient. Patent Document 2 discloses a technique of controlling the rate of etching by adjusting the temperature and Si vapor pressure.